Dynamic Routing of Voicemail Requests Using Location Information of Subscriber Device

A voicemail system is a computer-based system that allows users and subscribers to exchange personal voice messages, select and deliver voice information, and process transactions using a telephone. After voicemails are recorded, a voicemail server converts the voicemails into generic audio files that most mobile phones or computers will be able to play without a need for special software.

The technologies described herein will become more apparent to those skilled in the art from studying the Detailed Description in conjunction with the drawings. Embodiments or implementations describing aspects of the invention are illustrated by way of example, and the same references can indicate similar elements. While the drawings depict various implementations for the purpose of illustration, those skilled in the art will recognize that alternative implementations can be employed without departing from the principles of the present technologies. Accordingly, while specific implementations are shown in the drawings, the technology is amenable to various modifications.

In wireless communications, users use devices to initiate phone calls to other users. There are cases where phone calls do not reach a terminating party due to various reasons, such as a network failure preventing connection, radio paging issues, protocol issues, and/or impairments associated with a wireless network, devices, or transport. In such cases, an originating party that initiated the call is given an option to leave a voicemail for the terminating party. Traditionally, mobile network operators have multiple voicemail servers each associated with pre-designated subscribers. Each voicemail server has a pilot number such that each subscriber of the mobile network is pre-allocated to be associated with a single server. This creates inherent challenges for mobile network operators that are looking to provide efficient and proximate voicemail routing services for subscribers by causing delays in voicemail setup times and load imbalances across multiple voicemail servers,

The disclosed technologies address these and other problems of conventional mobile networks by using real-time or near real-time location information of callers to route voicemails to proximate voicemail servers for efficiency. Identification of location of callers can be done based on cell global identity (CGI) information. The CGI information is part of the Session Initiation Protocol (SIP) used for establishing voice calls or voicemail. Core network nodes initiating a call path towards voicemail servers can send a query to a Domain Name System (DNS) server that stores the CGI information. Upon receiving the query, the DNS server can look up the CGI information of callers to map locations of the callers to proximate voicemail servers. The output of the query includes information regarding proximate voicemail servers and is sent to the core network nodes, which can then select appropriate voicemail servers based on additional factors such as existing loads of the proximate voicemail servers and/or server status determined based on internal management algorithm. As a result, subscribers can benefit from faster voicemail setup time based on the routing techniques implemented.

The description and associated drawings are illustrative examples and are not to be construed as limiting. This disclosure provides certain details for a thorough understanding and enabling description of these examples. One skilled in the relevant technology will understand, however, that the invention can be practiced without many of these details. Likewise, one skilled in the relevant technology will understand that the invention can include well-known structures or features that are not shown or described in detail, to avoid unnecessarily obscuring the descriptions of examples.

is a block diagram that illustrates a wireless telecommunication network(“network”) in which aspects of the disclosed technology are incorporated. The networkincludes base stations-through-(also referred to individually as “base station” or collectively as “base stations”). A base station is a type of network access node (NAN) that can also be referred to as a cell site, a base transceiver station, or a radio base station. The networkcan include any combination of NANs including an access point, radio transceiver, gNodeB (gNB), NodeB, eNodeB (eNB), Home NodeB or Home eNodeB, or the like. In addition to being a wireless wide area network (WWAN) base station, a NAN can be a wireless local area network (WLAN) access point, such as an Institute of Electrical and Electronics Engineers (IEEE) 802.11 access point.

The NANs of a networkformed by the networkalso include wireless devices-through-(referred to individually as “wireless device” or collectively as “wireless devices”) and a core network. The wireless devices-through-can correspond to or include networkentities capable of communication using various connectivity standards. For example, a 5G communication channel can use millimeter wave (mmW) access frequencies of 28 GHz or more. In some implementations, the wireless devicecan operatively couple to a base stationover a long-term evolution/long-term evolution-advanced (LTE/LTE-A) communication channel, which is referred to as a 4G communication channel.

The core networkprovides, manages, and controls security services, user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The base stationsinterface with the core networkthrough a first set of backhaul links (e.g., S1 interfaces) and can perform radio configuration and scheduling for communication with the wireless devicesor can operate under the control of a base station controller (not shown). In some examples, the base stationscan communicate with each other, either directly or indirectly (e.g., through the core network), over a second set of backhaul links-through-(e.g., X1 interfaces), which can be wired or wireless communication links.

The base stationscan wirelessly communicate with the wireless devicesvia one or more base station antennas. The cell sites can provide communication coverage for geographic coverage areas-through-(also referred to individually as “coverage area” or collectively as “coverage areas”). The geographic coverage areafor a base stationcan be divided into sectors making up only a portion of the coverage area (not shown). The networkcan include base stations of different types (e.g., macro and/or small cell base stations). In some implementations, there can be overlapping geographic coverage areasfor different service environments (e.g., Internet-of-Things (IoT), mobile broadband (MBB), vehicle-to-everything (V2X), machine-to-machine (M2M), machine-to-everything (M2X), ultra-reliable low-latency communication (URLLC), machine-type communication (MTC), etc.).

The networkcan include a 5G networkand/or an LTE/LTE-A or other network. In an LTE/LTE-A network, the term eNB is used to describe the base stations, and in 5G new radio (NR) networks, the term gNBs is used to describe the base stationsthat can include mmW communications. The networkcan thus form a heterogeneous networkin which different types of base stations provide coverage for various geographic regions. For example, each base stationcan provide communication coverage for a macro cell, a small cell, and/or other types of cells. As used herein, the term “cell” can relate to a base station, a carrier or component carrier associated with the base station, or a coverage area (e.g., sector) of a carrier or base station, depending on context.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and can allow access by wireless devices that have service subscriptions with a wireless networkservice provider. As indicated earlier, a small cell is a lower-powered base station, as compared to a macro cell, and can operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Examples of small cells include pico cells, femto cells, and micro cells. In general, a pico cell can cover a relatively smaller geographic area and can allow unrestricted access by wireless devices that have service subscriptions with the networkprovider. A femto cell covers a relatively smaller geographic area (e.g., a home) and can provide restricted access by wireless devices having an association with the femto unit (e.g., wireless devices in a closed subscriber group (CSG), wireless devices for users in the home). A base station can support one or multiple (e.g., two, three, four, and the like) cells (e.g., component carriers). All fixed transceivers noted herein that can provide access to the networkare NANs, including small cells.

The communication networks that accommodate various disclosed examples can be packet-based networks that operate according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer can be IP-based. A Radio Link Control (RLC) layer then performs packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer can perform priority handling and multiplexing of logical channels into transport channels. The MAC layer can also use Hybrid ARQ (HARQ) to provide retransmission at the MAC layer, to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer provides establishment, configuration, and maintenance of an RRC connection between a wireless deviceand the base stationsor core networksupporting radio bearers for the user plane data. At the Physical (PHY) layer, the transport channels are mapped to physical channels.

Wireless devices can be integrated with or embedded in other devices. As illustrated, the wireless devicesare distributed throughout the system, where each wireless devicecan be stationary or mobile. For example, wireless devices can include handheld mobile devices-and-(e.g., smartphones, portable hotspots, tablets, etc.); laptops-; wearables-; drones-; vehicles with wireless connectivity-; head-mounted displays with wireless augmented reality/virtual reality (AR/VR) connectivity-; portable gaming consoles; wireless routers, gateways, modems, and other fixed-wireless access devices; wirelessly connected sensors that provides data to a remote server over a network; IoT devices such as wirelessly connected smart home appliances, etc.

A wireless device (e.g., wireless devices-,-,-,-,-,-, and-) can be referred to as a user equipment (UE), a customer premise equipment (CPE), a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a handheld mobile device, a remote device, a mobile subscriber station, terminal equipment, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a mobile client, a client, or the like.

A wireless device can communicate with various types of base stations and networkequipment at the edge of a networkincluding macro eNBs/gNBs, small cell eNBs/gNBs, relay base stations, and the like. A wireless device can also communicate with other wireless devices either within or outside the same coverage area of a base station via device-to-device (D2D) communications.

The communication links-through-(also referred to individually as “communication link” or collectively as “communication links”) shown in networkinclude uplink (UL) transmissions from a wireless deviceto a base station, and/or downlink (DL) transmissions from a base stationto a wireless device. The downlink transmissions can also be called forward link transmissions while the uplink transmissions can also be called reverse link transmissions. Each communication linkincludes one or more carriers, where each carrier can be a signal composed of multiple sub-carriers (e.g., waveform signals of different frequencies) modulated according to the various radio technologies. Each modulated signal can be sent on a different sub-carrier and carry control information (e.g., reference signals, control channels), overhead information, user data, etc. The communication linkscan transmit bidirectional communications using frequency division duplex (FDD) (e.g., using paired spectrum resources) or Time division duplex (TDD) operation (e.g., using unpaired spectrum resources). In some implementations, the communication linksinclude LTE and/or mmW communication links.

In some implementations of the network, the base stationsand/or the wireless devicesinclude multiple antennas for employing antenna diversity schemes to improve communication quality and reliability between base stationsand wireless devices. Additionally or alternatively, the base stationsand/or the wireless devicescan employ multiple-input, multiple-output (MIMO) techniques that can take advantage of multi-path environments to transmit multiple spatial layers carrying the same or different coded data.

In some examples, the networkimplements 6G technologies including increased densification or diversification of network nodes. The networkcan enable terrestrial and non-terrestrial transmissions. In this context, a Non-Terrestrial Network (NTN) is enabled by one or more satellites such as satellites-and-to deliver services anywhere and anytime and provide coverage in areas that are unreachable by any conventional Terrestrial Network (TN). A 6G implementation of the networkcan support terahertz (THz) communications. This can support wireless applications that demand ultrahigh quality of service requirements and multi-terabits per second data transmission in the 6G and beyond era, such as terabit-per-second backhaul systems, ultrahigh-definition content streaming among mobile devices, AR/VR, and wireless high-bandwidth secure communications. In another example of 6G, the networkcan implement a converged Radio Access Network (RAN) and Core architecture to achieve Control and User Plane Separation (CUPS) and achieve extremely low User Plane latency. In yet another example of 6G, the networkcan implement a converged Wi-Fi and Core architecture to increase and improve indoor coverage.

is a block diagram that illustrates an architectureincluding 5G core network functions (NFs) that can implement aspects of the present technology. A wireless devicecan access the 5G network through a NAN (e.g., gNB) of a RAN. The NFs include an Authentication Server Function (AUSF), a Unified Data Management (UDM), an Access and Mobility management Function (AMF), a Policy Control Function (PCF), a Session Management Function (SMF), a User Plane Function (UPF), and a Charging Function (CHF).

The interfaces N1 through N15 define communications and/or protocols between each NF as described in relevant standards. The UPFis part of the user plane and the AMF, SMF, PCF, AUSF, and UDMare part of the control plane. One or more UPFs can connect with one or more data networks (DNs). The UPFcan be deployed separately from control plane functions. The NFs of the control plane are modularized such that they can be scaled independently. As shown, each NF service exposes its functionality in a Service Based Architecture (SBA) through a Service Based Interface (SBI)that uses HTTP/2. The SBA can include a Network Exposure Function (NEF), a NF Repository Function (NRF)a Network Slice Selection Function (NSSF), and other functions such as a Service Communication Proxy (SCP).

The SBA can provide a complete service mesh with service discovery, load balancing, encryption, authentication, and authorization for interservice communications. The SBA employs a centralized discovery framework that leverages the NRF, which maintains a record of available NF instances and supported services. The NRFallows other NF instances to subscribe and be notified of registrations from NF instances of a given type. The NRFsupports service discovery by receipt of discovery requests from NF instances and, in response, details which NF instances support specific services.

The NSSFenables network slicing, which is a capability of 5G to bring a high degree of deployment flexibility and efficient resource utilization when deploying diverse network services and applications. A logical end-to-end (E2E) network slice has pre-determined capabilities, traffic characteristics, service-level agreements, and includes the virtualized resources required to service the needs of a Mobile Virtual Network Operator (MVNO) or group of subscribers, including a dedicated UPF, SMF, and PCF. The wireless deviceis associated with one or more network slices, which all use the same AMF. A Single Network Slice Selection Assistance Information (S-NSSAI) function operates to identify a network slice. Slice selection is triggered by the AMF, which receives a wireless device registration request. In response, the AMF retrieves permitted network slices from the UDMand then requests an appropriate network slice of the NSSF.

The UDMintroduces a User Data Convergence (UDC) that separates a User Data Repository (UDR) for storing and managing subscriber information. As such, the UDMcan employ the UDC under 3GPP TS 22.101 to support a layered architecture that separates user data from application logic. The UDMcan include a stateful message store to hold information in local memory or can be stateless and store information externally in a database of the UDR. The stored data can include profile data for subscribers and/or other data that can be used for authentication purposes. Given a large number of wireless devices that can connect to a 5G network, the UDMcan contain voluminous amounts of data that is accessed for authentication. Thus, the UDMis analogous to a Home Subscriber Server (HSS), to provide authentication credentials while being employed by the AMFand SMFto retrieve subscriber data and context.

The PCFcan connect with one or more application functions (AFs). The PCFsupports a unified policy framework within the 5G infrastructure for governing network behavior. The PCFaccesses the subscription information required to make policy decisions from the UDM, and then provides the appropriate policy rules to the control plane functions so that they can enforce them. The SCP (not shown) provides a highly distributed multi-access edge compute cloud environment and a single point of entry for a cluster of network functions, once they have been successfully discovered by the NRF. This allows the SCP to become the delegated discovery point in a datacenter, offloading the NRFfrom distributed service meshes that make-up a network operator's infrastructure. Together with the NRF, the SCP forms the hierarchical 5G service mesh.

The AMFreceives requests and handles connection and mobility management while forwarding session management requirements over the N11 interface to the SMF. The AMFdetermines that the SMFis best suited to handle the connection request by querying the NRF. That interface and the N11 interface between the AMFand the SMFassigned by the NRF, use the SBI. During session establishment or modification, the SMFalso interacts with the PCFover the N7 interface and the subscriber profile information stored within the UDM. Employing the SBI, the PCFprovides the foundation of the policy framework which, along with the more typical QoS and charging rules, includes Network Slice selection, which is regulated by the NSSF.

A voicemail system is a computer-based system that allows users and subscribers to exchange personal voice messages and to select and deliver voice information. Under the Session Initiation Protocol (SIP), voicemail servers are identified by a Uniform Resource Identifier (URI), similar to other resources such as user agents, call routers.is a flowchart representation of an example call flow of a SIP session between user deviceand user devicebeing redirected to a voicemail server. The call flowcomprises, at Operation, sending, by the user device, an INVITE request to a SIP nodethat is responsible for initiating the SIP session. At Operation, immediately after receiving the INVITE request from the user device, the SIP nodesends a Trying response to the user deviceto stop re-transmissions of the INVITE request.

At Operation, the SIP nodesearches the address of user device. The SIP nodecan communicate with a location server or a database to obtain the address of user device. In some implementations, Operationinvolves the SIP nodetransmitting a voicemail routing request to the database. The voicemail routing request can be configured to identify the user deviceand/or a user profile associated with the user device. In response to the voicemail routing request, the database can generate a voicemail routing response that includes a voicemail routing profile based on the user profile associated with the user device. At Operation, after obtaining the address of user device, the SIP nodeforwards the INVITE request to the user device.

At Operation, a failure response is generated and sent to the SIP node. The failure response can be generated in various circumstances, including request failures due to the user devicefailing to establish the SIP session by missing or rejecting a call, server errors, and/or global failures. At Operation, the SIP nodeforwards the failure response to the user device.

At Operation, because the user deviceis unavailable, the SIP nodesends an INVITE request to the voicemail serverto redirect the SIP session to the voicemail server. At Operation, the voicemail serversends an OK response to the SIP node, which is forwarded to the user device.

At Operation, the user devicesends an ACK to the SIP node, which is forwarded to the voicemail server. The ACK confirms the INVITE request and establishes the session between the user deviceand the voicemail server. At Operation, real-time transport (RTP) packets start flowing between the user deviceand the voicemail server, which indicates an on-going communication between the user deviceand the voicemail server. The communication can include a voicemail deposit session with the voicemail serverwherein the user deviceis enabled to deposit a voicemail for the user devicein the voicemail server.

At any time during the session, the user devicecan terminate the session by sending a BYE request. At Operation, the user devicesends the BYE request to the SIP node, which forwards the BYE request to the voicemail server. At Operation, the voicemail serversends an OK response to the SIP nodeto confirm the BYE request, effectively terminating the session. The OK response is forwarded to the user device.

In some cases, a user device is busy or unavailable to establish the call session requested by a mobile network. In other cases, the mobile network fails to reach the user device due to various challenges, such as radio paging issues, protocol issues, and/or impairments within the mobile network, user device, or transport. In some implementations, unanswered communication sessions, such as the session illustrated in, are routed to a voicemail server associated with a mobile network.

is a block diagram that illustrates a network that utilizes cellular network infrastructure to receive communication session requests from user devices and forward unanswered communication session requests to voicemail servers. As illustrated in, the networkincludes communication serversA-C that operate as platforms for communication applications. The networkalso includes multiple databasesA-C which store various types of data including, but not limited to, call-detail data, network data, and subscriber data. The networkis not limited to the depicted network nodes and can also include additional access networks, network nodes, and network functions not depicted in the diagram. As explained in relation withabove, a user devicecan send a request to initiate an SIP session with another mobile device, such as a user device. When the request to initiate the SIP session goes unanswered, a network access nodeof a networkcan redirect the SIP session to a voicemail server associated with the network.

Traditionally, mobile network operators have multiple voicemail servers, such as the voicemail serversA-D illustrated in, each associated with pre-assigned subscribers. When a subscriber joins the mobile network, the mobile network operator assigns a static voicemail routing number, also known as a voicemail pilot number, to the subscriber. The static voicemail routing number is assigned for each subscriber who is identified via each subscriber's Mobile Station International Subscriber Directory Number (MSISDN), and each static voicemail routing number is associated with one of the voicemail servers of the mobile network. Mobile network operators assign static voicemail routing numbers in order to distribute subscribers across available voicemail routing numbers to realize balanced distribution of traffic load among existing voicemail servers.

For example, referring to, a mobile network operator has a total of 4 million subscribers. In order to evenly distribute the subscribers among the four voicemail servers, the mobile network operator can assign static voicemail routing number A to user profiles of 1 million subscribers. Subscribers who are assigned voicemail routing number A are routed to voicemail serverA. Similarly, the mobile network operator assigns static voicemail routing number B to user profiles of 1 million other subscribers, whose voicemail requests are routed to voicemail serverB. The mobile network operator can assign voicemail routing numbers C and D to the remaining 2 million subscribers in a similar fashion, thereby assigning an equal number of subscribers to each voicemail server.

However, such an approach has a number of drawbacks. First of all, having a balanced split of subscribers across available voicemail routing numbers is difficult to achieve because provisioning of new subscribers is performed much earlier in the mobile network before the subscribers get onboard with a mobile carrier. Second, this approach fails to take into account latency issues that can arise due to subscribers being assigned to voicemail servers that are located distant from the subscribers. For example, referring back to the example above, the mobile network operator assigns static voicemail routing number A to a subscriber residing in California. The voicemail serverA associated with the static voicemail routing number A is located in Virginia, whereas the voicemail serverB is located in California. Due to varying distances between the location of the subscriber an the voicemail servers, the subscriber residing in California would experience less latency and faster setup time if the subscriber's voicemail requests were routed to the voicemail serverB. The above approach of evenly distributing subscribers among existing voicemail routing numbers ignores such geographical advantages.

In another example, a subscriber who initially subscribed to the mobile network in New York relocates from New York to Seattle while retaining the MSISDN. When the subscriber initiates a voicemail request, the request is routed to a voicemail server based in New York because the subscriber was originally assigned a static voicemail routing number associated with the voicemail server based in New York.

Unbalanced load distribution across various voicemail servers can push loads in some voicemail servers to the point of maximum utilization and cause congestions and timeouts in extreme cases. In such situations, the mobile networks operators have to reevaluate which of the voicemail servers provides optimal and efficient services to the affected subscribers.

The disclosed technologies address possible drawbacks, e.g., routing latencies, of existing voicemail routing processes by proposing a different voicemail routing technique. Specifically, the voicemail routing technique involves routing a voicemail request to a voicemail server that is geographically close to the subscriber that initiates the voicemail requests using the CGI information stored in the P-ANI header to map and select voicemail servers based on geographic proximity. Traditional voicemail routing techniques require prior storing of a voicemail routing profile associated with a user device initiating a voicemail request in a database. Upon receiving a voicemail request, the voicemail request is transmitted to the database to retrieve the stored voicemail routing profile, which is subsequently used to establish a voicemail session. The techniques described herein can be implemented in various embodiments to eliminate the need for storing voicemail profiles or similar provisioning of voicemail services. Instead, the disclosed techniques provide voicemail routing based on real-time or near real-time location information of a subscriber associated with the voicemail request. In some implementations, the voicemail routing technique involves utilizing load information associated with one or more voicemail servers to determine preferred geographically proximate voicemail servers with loads below a threshold.

is a flowchart representation of an example process for routing voicemail requests to proximate voicemail servers in accordance with one or more embodiments of the present technology. Other implementations of the processinclude additional, fewer, or different steps or performing the steps in different orders.

At Operation, a core network nodereceives a voicemail request associated with a user devicefrom a wireless communication node. The core network noderefers to any core network node that can initiate a call path towards one or more voicemail servers. The core network nodecan be a telephony application server (TAS), a media gateway control function (MGCF), or a breakout gateway control function (BGCF), depending on the configuration of the mobile network.

At Operation, after receiving the voicemail request associated with the user device, the core network nodesends a query to the DNS serverto identify a voicemail server based on the location of user deviceassociated with the voicemail request. The query includes CGI information of the user device. The core network nodesends the query to the DNS serverbecause the core network nodedoes not have the capability to translate the CGI information to the geographic location of the user device.

In some implementations, within the SIP framework is an information element called Primary-Access Network Information (P-ANI) header that includes CGI information associated with the user device. The CGI information includes cell site information of a serving cell the user deviceis camped in. A relative location of the user devicecan be determined using the CGI information of the serving cell which is providing services to the user device.

At Operation, upon receiving the query from the core network nodes, the DNS serveridentifies proximate voicemail servers for the user deviceusing the CGI information in the query and information stored in the DNS server. In some implementations, the DNS serverincludes one or more location mapping tables and/or one or more pre-define logic to determine a voicemail server proximate to the user device. Using the information stored in the DNS serverand the CGI information in the received query, the DNS servercan identify the location of the user deviceand subsequently identify one or more voicemail servers that are proximate to the user device.

In an example, the DNS serveridentifies that the user deviceis located in Orange County, California. Based on the identified location, the DNS serveridentifies a voicemail server located in Orange County, followed by voicemail servers located in neighboring counties, such as Los Angeles County and Riverside County, which can be used if the voicemail server located in Orange County is unresponsive. In other implementations, other standards for geographic proximity are applied. Geographically proximate servers can refer to voicemail servers within the same city, the same county, the same state, or a group of states making up a region as the user device.

In some embodiments, at Operation, the DNS serverobtains load information associated with the one or more voicemail servers that are proximate to the user device. For example, a mechanism can be implemented such that the DNS serverperiodically receives load information associated with each voicemail server. The mechanism triggers an alert if the number of consecutive missed reports from a given voicemail server to the DNS serverexceeds a pre-determined threshold value. In another example, the load information is obtained only in response to a trigger, such as a DNS query from the DNS server to the voicemail server. In some implementations, the DNS serverkeeps track of responses to the DNS query to calculate a history of load information for the one or more voicemail servers.

At Operation, the DNS serversends a query output to the core network node. In some implementations, the query output includes one or more voicemail servers that are proximate to the user device. In other implementations, the query output is a list of voicemail servers ranked based on geographic proximity to the user device. In some implementations, the query output sent by the DNS serverincludes load information obtained by the DNS serverbased on communication with the one or more voicemail servers.

At Operation, the core network nodedetermines one or more proximate voicemail servers based on the query output. After determining the voicemail serveras the voicemail server that is geographically closest to the location of the user devicebased on the query output, the core network nodeproceeds to Operation, initiating a voicemail session between the user deviceand the voicemail server. During the voicemail session, the user deviceis enabled to deposit a voicemail.

In some implementations, in determining the one or more proximate voicemail servers, the core network node takes load balance into consideration. After examining the load information associated with the one or more proximate voicemail servers and determining that the load associated with the voicemail serveris below a pre-determined threshold, the core network nodeproceeds to Operationto initiate a voicemail session between the user deviceand the voicemail server. In another example, upon receiving a list of proximate voicemail servers and determining that a voicemail server closest to the location of the user devicehas reached a point of overload, the core network nodeselects a voicemail server second closest to the location of the user deviceafter confirming that the load has not exceeded the pre-determined threshold.

In other implementations, the core network nodedetermines that the load information associated with the voicemail serveris outdated, or that more information is needed before establishing connection. In such cases, the core network nodecan communicate with the voicemail serverto receive additional load information. The additional load information can indicate that the load of the voicemail serverhas exceeded the pre-determined threshold. In such a situation, the core network nodesends another query to the DNS serverto reallocate DNS mapping to redistribute the load and identify another voicemail server in geographic proximity with the user devicewhose load has not exceeded the pre-determined threshold.